PID Control for HVAC Systems

Smart control schemes have allowed building operators access to increasingly granular control and monitoring of building systems unlocking increased building efficiency and customization. Among the existing smart control schemes, the Proportional, Integral, Derivative (PID) controller is by far the most widely implemented.

What is a PID Controller?

A PID controller uses a closed loop PID algorithm which compares a setpoint value to a feedback value with the goal of adjusting the output of the algorithm in a way which minimizes the difference between the setpoint and feedback values, commonly referred to as “error”. 

The PID algorithm consists of three mathematical terms, proportional, integral, and derivative, each having an associated constant that allows the algorithm to be tuned to achieve the desired system behavior. 

– The proportional term affects how the system reacts to the magnitude of the error. 

– The integral term minimizes the sum of the error over time. This term helps prevent hysteresis. 

– The derivative term affects how quickly the feedback value is allowed to change which effectively adds “friction” to the control scheme. 

Adjusting the constants associated with each term changes the magnitude of the effect each term has on the output of the algorithm; therefore, the overall system behavior.

Where is PID used in HVAC?

PID controllers are used in many places within an HVAC system. Layers upon layers of PID controllers manage everything from the pressure & temperature of the air in ductwork to ensuring the correct airflow through each terminal unit. Ultimately, the temperature, humidity, and even pressure within a room is maintained using a symphony of PID controllers. 

EAB Training strives to provide students with a thorough understanding of basic PID controller concepts so students can identify problems caused by PID tuning deficiencies they may encounter in the field. 

Interested in the TAB Control Systems Verification course or EAB Training? Fill out an interest form!

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